Scale projection means for weighing balances



Patented Jan. 3, 1950 SCALE PROJECTION MEAN S FOR WEIGHING BALAN CES Sydney Rayner Green, Barkingside, Ilford, England Application December 23, 1947, Serial No. 793.366 In Great Britain May 27, 1946 Section 1, Public Law 690, August 8, 1946 Patent expires May 27, 1966 6 Claims.

This invention relates to weighing balances more particularly of the type for accurate weighing such as fine balances, projected scale, aperiodio or delicate balances.

In balances of the type in question there 'are a number of features which are not altogether satisfactory in practice &and it is the object of the present invention to provide various improvements by which such disadvantages are eliminated.

It has been the practice hitherto to mount the viewing screen `at the upper part of the case. Such position is rather inconvenient and one object of the present invention is to provide an improved arrangement of the scaie -projecting means whereby-the screen may be located at the base or pan level.

On known viewing screens it is usual to engrave a -vernier scale on the screen :for the purpose of -subdividing projected division of the scale. Such Verniers are somewhat -diflicult to read and it is a further object of the invention to 'provide improved micrometer reading means which are located apart from the screen so that they may be read with ease.

Further, in known means for adjusting the index line on the screen such have been arranged at the top of the case 'and a further object of the present invention is to provide adjusting means operable from the base position giving quicker and easier manipulation.

According to one feature -oi' the invention the viewing screen assembly is located at the base of the cage 'and the scale projection means include reflecting means whereby the scale is projected downwardly on to the screen assembly.

According to another feature improved vernier means providing sub-divisions of a division projected on the screen ;are mounted adjacent the screen assembly and preferably below the case and are operatively geared to the index line.

The Vernier means may comprise a rotary dial or disc having ten equal graduations corresponding to one projected division on its upper face sand a zero indicating arm or finger coaxial with the dial.

The rotary dial may be used for zero setting the index line as seen on the screen and the indicating arm may be frictionally controlled in its adjustments.

In the accompanying drawings:

The figure is a sectional side elevation of the improved viewing screen assembly according to the invention.

In carrying the invention into efrect according to one convenient mode by Way of example, a base I ormed of glass or other suitable material is provided at the rear with a hollow support or pillar 2 by 'which the beam and scale system is supported in known way. Adjacent the lower end the pillar is perforated at 3 so that a beam of light from a, suitable source located to the rear of the `pill ar will pass through on to a grati cule 4.

Adjacent the front of the base a viewing screen assembly is provided comprising a box or casing 5 having a metal rear wall 6, an upper pl'ain glass top 'I and a forward sloping'matt glass screen 8. The rear wall B supports a tube 9 at the level of the graticule and in which a suitable magnifying lens system ID is carried. Within the tube an adjustable angle mirror ll is provided by which la magnified image of the illuminated portion of the -graticule is reected upwardly through an aperture l2 in the tube and on to a mirror !3 which is supported by the pill ar 2.

From the upper mirror |3 the image is refiected downwardly through the plain glass top 1 of the screen box and on to an adjustable angle mirror 14 located within the box. The image is reflected from this mirror I4 on to the sloping matt screen 8.

Located to the rear of the screen 8 and parallel t-o the plane thereof is an index Wire [5 which is supported in a suitable frame !6 carri-ed by a horizontal bar l'l so that it may slide thereon. The rame or a part 18 secured thereto depends vertically down ward and such part carries a rack l9 with which a pinion 20 meshes. The pinion 20 is secured to the u pper end of a spindle 2l which has hearing means 22 extending through the g1=ass base I.

At its lower end and beneath the base I the spindle 2! earries a disc or dial *23 by which the spindle may be rotated and through the pinion 20 and rack !9 cause the index line 15 to be adjusted across the screen 8.

Between the disc 23 and the under surface of the base l a rotary indicating or zero arm 24 is mounted by means of a sleeve 25 which is screwed upon the spindle hearing means 22. The indicating arm 24 is freely rotatable on the sleeve 25 and is held stationary frictionally by means of a suitable 'spring 26 .between the arm and the base.

The indicating arm 24 at its outer end is inclined downwardly into close proximity to the upper surface of the disc. The arm is also provided with an upstanding peg 38 by which it may ibe moved about its pivot.

The rotary disc 23 and indicating arm '24 are adapted to provide vernier means by which subconforms to a movement of ten divisions 'fthe' disc 23 relatively to the indicating arm or: pointer 24.

By means of the rotary disc 23 the zeroising of the index line 15 may be"i'adily' eeted -nd in combination with the indicating 'arni 2'4` the" appropriate sub-divisions of a projctect division may readily be determined by moving their idexing line !5 after a weighing operationandmeading off the divisions on the disc against the'indicating arm or pointer.

In" rde'r to avoid back'lash* "between the i'ck lg'nd pinio `20 a' s'pring 21' may-be provided s'ecured at'bn' end to"the`p'art 'l8' and at'the 'other t`the"rear"wan 6." As'ar' 'alternative a 'iiatspring may be providedbetween'the part !8 a'h'd .merrem-wen 28 ofthe casing 5.

i Accordingto a mo'difie'd'fo-rm th disc"23"'and arm ma'y b dispen'sedwith and "a knob mounted upon the`spihd1'e` 2l. V

l-thdlgh it 'is pre-fama to 'reet the image of 'ai thescale downwatdly o'n t`` the screen as'smbly,

n -refiected upwardiy through the iowerpart'of the a rear -waii which would be-formed of -plain glass foi' the purpose.

. l l n 'a we'ighing-balance of 'the typedescribed, I comprising ascale system inchding a: beam, a

graticule carriedrb'y the b'eam", acase including "ashppcirting:` base, 'a' viewing screenassembly 10- 2 bated at andsupported on" said base:- *said :assemmblyscmprising a 'casing having a rear wa-11, a 'scveen mounted insaid casin'g, 'a lens tube'-mounted on 'said rear wali and in front of said graticule:

22 Aweighing balanceas claimed iriclaim 1, wherein 'a rame is locatedin 'thez casing atnthe t rear' of the -screen; said' frame having an index refie'cted'by said mirrors on to the s'creen-by the` line and means for adjusting the frame along a horizontal axis, Vernier means located beneath the supporting base, and means coupling the verniermeans with the'adjusting means.

5 3. A weighing balance' asl claifmed. in claim 2,

Wherein the frame is mo unted for sliding moves: ment on a horizontal bar Secured to the casing,

said frame having a rack meshing with a pinion 'operatively connected to the vernier means.

10 4. A weghing balance as claimed in claim 3, wherein a-spindle extends through the base and said pinion is Secured to the upper end thereof,

the lower end of the spindie being secured to a dial having verniei* divisions on its upper surface,

and'a'zero indicating arm coaxial with the spindle.

5: A weighing balance as claimed in claim 4, z whe'rein a hearing sleeve extends through the base and forms a bearing for the spindle, said zero indicating arm being mounted for rotation on the lower end of the sieeve, and riction means ior'h'olding the' arm in'its adjusted position.

61 In 'a'weighing-balance eithetypdesribed "eo'npri'sing ascale system'inciuding 'a"be'am, a graticuie carried by the' beam,a supporting'base, a viewing'screen' ass'm'bly includinga scren'icated at 'and lsupported on Said base', alien's system for projectingan image" of 'said gia'ti'culebnto said screen an index line lo'cated`adj acnt the screen,

means for moving the index line across. the screen, vernier means located beneathand. supported by V I said base, and-meaIis-copling the vernien means by a suitable arrangement of `mrrors tm'ay be t and .said meansor moving theiindexvin 7 SYDNEY- 'RAYNER GREEN.

. EEFERENCES CI IIED 'Ijhe following references are 'of- `record in--the file' of' this patent:

" UNITED STAT-ES ..PA 'I'NTS i Katz `2Jun'e 6, 1944 

